Lysophospholipid acyltransferases: novel potential regulators of the inflammatory response and target for new drug discovery

Untargeted metabolomics combined with pseudotargeted lipidomics revealed the metabolite profiles of blood-stasis syndrome in type 2 diabetes mellitus

Objective

Blood-stasis syndrome (BSS), an important syndrome in Type 2 diabetes mellitus(T2DM), is associated with the pathophysiological mechanisms underlying diabetic vascular complications. However, BSS has not been fully characterized as of yet. Due to the strong correlation between BSS and vasculopathy, we hypothesized that the metabolic characteristics of BSS in T2DM (T2DM BSS) are highly specific. By combining untargeted metabolomics and pseudotargeted lipidomics approaches, this study aimed to comprehensively elucidate the metabolic traits of T2DM BSS, thereby providing novel insights into the vascular complications of diabetes and establishing a foundation for precision medicine.

Methods

The survey was conducted in Haidian District of Beijing from October 2021 to November 2021, and data collection was completed in January 2022. Liquid chromatography-mass spectrometry (LC-MS) based untargeted metabolomics and liquid chromatography-tandem mass spectrometry (LC-MS/MS) based pseudotargeted lipidomics were performed to detect metabolites and lipids. Multivariate, univariate, and pathway analyses were utilized to investigate metabolic changes. The unique metabolites of BSS were obtained by inter-group comparisons and screening. Receiver operating characteristic (ROC) curve analysis was performed to evaluate the diagnostic accuracy of metabolites.

Results

A total of 1189 participants completed the survey, of which 120 participants were recruited in this study and further divided into a discovery cohort (n = 90) and a validation cohort (n = 30). Among these, 21 participants were selected for psuedotargeted lipidomics analysis. 81 metabolites, mainly involving glycerophospholipids, were identified as unique metabolites of T2DM BSS, while fatty acyls (FAs) were identified as unique lipids. T2DM BSS was associated with significant dysregulation in glycerophospholipid metabolism and choline metabolism within cancer pathways as major metabolic disturbances. Furthermore, analyses of both the discovery and validation cohorts, indicated that LysoPC (20:5(5Z,8Z,11Z,14Z,17Z)/0:0) and LysoPC (15:0) had the greatest impact on distinguishing BSS.

Conclusion

Altered levels of glycerophospholipids and FAs have been associated with T2DM BSS. These results provide valuable mechanistic insights linked with the development of BSS in T2DM subjects.

The combination of Brassica rapa L. polysaccharides and cisplatin enhances the anti liver cancer effect and improves intestinal microbiota and metabolic disorders

Polysaccharides are commonly used as low-toxicity anticancer active substances to enhance the chemotherapeutic effect of cisplatin and reduce toxicity. Brassica rapa L. polysaccharides have been shown to have hepatoprotective effects; however, their anticancer effects in combination with cisplatin and their mechanisms have not been reported. An acidic polysaccharide from Brassica rapa L. (BRCPe) using hydroalcohol precipitation-assisted sonication was Characterized. The effects of BRCPe combined with cisplatin treatment on tumor growth in hepatocellular carcinoma mouse model were investigated. The impact of the combined treatment on the composition of intestinal flora, levels of short-chain fatty acids and endogenous metabolites in tumor mice were analyzed based on macrogenomic and metabolomic data Our results showed that the BRCPe combined with low-dose Cisplatin group showed better inhibitory activity against hepatocellular carcinoma cell growth in terms of tumor volume, tumor weight, and tumor suppression rate compared with the BRCPe and Cisplation alone group, and reduced the side effects of cisplatin-induced body weight loss, immune deficiency, and liver injury. Furthermore, BRCPe combined with cisplatin was found to induce apoptosis in hepatocellular carcinoma cell through the activation of the caspase cascade reaction. In addition, the intervention of BRCPe were observed to modulate the composition, structure and functional structure of intestinal flora affected by cisplatin. Notably, Lachnospiraceae bacteria, Lactobacillus murinus, Muribaculaceae, and Clostridiales bacteria were identified as significant contributors to microbial species involved in metabolic pathways. Moreover, BRCPe effectively regulate the metabolic disorders in cisplatin-induced hepatocellular carcinoma mice. In conclusion, BRCPe could potentially function as an adjuvant or dietary supplement to augment the effectiveness of cisplatin chemotherapy through the preservation of a more efficient intestinal microenvironmental homeostasis.

Biomarkers of ulcerative colitis disease activity CXCL1, CYP2R1, LPCAT1, and NEU4 and their relationship to immune infiltrates

The diagnosis and assessment of ulcerative colitis (UC) poses significant challenges, which may result in inadequate treatment and a poor prognosis for patients. This study aims to identify potential activity biomarkers for UC and investigate the role of infiltrating immune cells in the disease. To perform gene set enrichment analysis, we utilized the cluster profiler and ggplot2 packages. Kyoto encyclopedia of genes and genomes was used to analyze degenerate enrichment genes. Significant gene set enrichment was determined using the cluster profiler and ggplot2 packages. Additionally, quantitative PCR (qRT-PCR) was employed to validate the expression of each marker in the ulcerative colitis model. We identified 651 differentially expressed genes (DEGs) and further investigated potential UC activity biomarkers. Our analysis revealed that CXCL1 (AUC = 0.710), CYP2R1 (AUC = 0.863), LPCAT1 (AUC = 0.783), and NEU4 (AUC = 0.833) were promising activity markers for the diagnosis of UC. Using rat DSS model, we validated these markers through qRT-PCR, which showed statistically significant differences between UC and normal colon mucosa. Infiltrating immune cell analysis indicated that M1 macrophages, M2 macrophages, activated dendritic cells (DCs), and neutrophils played crucial roles in the occurrence and progression of UC. Moreover, the activity markers exhibited varying degrees of correlation with activated memory CD4 T cells, M0 macrophages, T follicular helper cells, memory B cells, and activated DCs. The potential diagnostic genes for UC activity, such as CXCL1, CYP2R1, LPCAT1, and NEU4, as well as the infiltration of immune cells, may contribute to the pathogenesis and progression of UC.

Revealing the mechanism of raw and vinegar-processed Curcuma aromatica Salisb. [Zingiberaceae] regulates primary dysmenorrhea in rats via integrated metabolomics

Primary dysmenorrhea (PDM) is a common disorder among women around the world. Two processed products of Curcuma aromatica Salisb. [Zingiberaceae] (CAS) are traditional Chinese medicine (TCM) that have long been used to treat gynecological blood stasis syndrome such as primary dysmenorrhea. The mechanisms and active substances of CAS are still largely unknown. The study aimed to establish a rat model of primary dysmenorrhea which investigates the differences between the pharmacodynamics and mechanisms of raw CAS (RCAS) and vinegar-processed CAS (VCAS). Histopathology, cytokinetics, and metabolomics were adopted to evaluate the anti-blood stasis effect of RCAS and VCAS. In metabolomics, endogenous differential metabolites in plasma, urine, and feces are the essential steps to evaluate the effect of RCAS and VCAS. In this study, the rat model of primary dysmenorrhea was successfully established. After RCAS and VCAS intervention, the uterine tissue morphology of dysmenorrhea model rats was improved, and gland hypertrophy and myometrial hyperplasia were reduced as well as neutrophil content. Compared with the RCAS group, the VCAS group had better uterine morphology, few inflammatory factors, and significantly improved amino acid and lipid metabolism. The aforementioned results support the conclusion that VCAS performed better than RCAS in primary dysmenorrhea and that vinegar processing increases the efficacy of CAS.

Transcriptome analysis of Pacific white shrimp (Litopenaeus vannamei) hepatopancreas challenged by Vibrio alginolyticus reveals lipid metabolic disturbance

Vibrio alginolyticus is a devastating bacterial pathogen of Pacific white shrimp (Litopenaeus vannamei), which often causes acute hepatopancreatic necrosis syndrome (AHPNS) and early mortality syndrome (EMS). Elucidation of molecular mechanisms of L. vannamei in responding to infection is essential for controlling the epidemic. In the present study, transcriptomic profiles of L. vannamei hepatopancreas were explored by injecting with PBS or V. alginolyticus. Hepatopancreas morphology of L. vannamei was also assessed. The result reveals that compared with the hepatopancreas of PBS group, the storage cells (R-cell), secretory cells (B-cell) and star-shaped polygonal structures of the lumen were disappeared and necrotic after challenged by V. alginolyticus at 24 h. Transcriptome data showed that a total of 314 differential expression genes were induced by V. alginolyticus, with 133 and 181 genes up- and down-regulated, respectively. These genes were mainly associated with lysosome pathway, glycerophospholipid metabolism, drug metabolism-other enzymes, cysteine and methionine metabolism, aminoacyl-tRNA biosynthesis and PPAR signal pathway. Among these pathways, the lysosome pathway, glycerophospholipid metabolism and PPAR signal pathway were both related with lipid metabolism. Therefore, we detected the lipid accumulation in hepatopancreas by Oil Red O staining, TG and CHOL detection and the relative mRNA expression of several lipid metabolism related genes in the hepatopancreas of shrimp after challenge to V. alginolyticus. The present data reveals that lipids from the L. vannamei are nutrient sources for the V. alginolyticus and define the fate of the infection by modulating lipid homeostasis. These findings may have important implication for understanding the L. vannamei and V. alginolyticus interactions, and provide a substantial dataset for further research and may deliver the basis for preventing the bacterial diseases.

Effect of Helicobacter Pylori on Plasma Metabolic Phenotype in Patients With Gastric Cancer

BACKGROUND

Although Helicobacter pylori (Hp) as high risk factor for gastric cancer have been investigated from human trial, present data is inadequate to explain the effect of Hp on the changes of metabolic phenotype of gastric cancer in different stages.

PURPOSE

Herein, plasma of human superficial gastritis (Hp negative and positive), early gastric cancer and advanced gastric cancer analyzed by UPLC-HDMS metabolomics can not only reveal metabolic phenotype changes in patients with gastric cancer of different degrees (30 Hp negative, 30 Hp positive, 20 early gastric cancer patients, and 10 advanced gastric cancer patients), but also auxiliarily diagnose gastric cancer.

RESULTS

Combined with multivariate statistical analysis, the results represented biomarkers different from Hp negative, Hp positive, and the alterations of metabolic phenotype of gastric cancer patients. Forty-three metabolites are involved in amino acid metabolism, and lipid and fatty acid metabolism pathways in the process of cancer occurrence, especially 2 biomarkers glycerophosphocholine and neopterin, were screened in this study. Neopterin was consistently increased with gastric cancer progression and glycerophosphocholine tended to consistently decrease from Hp negative to advanced gastric cancer.

CONCLUSION

This method could be used for the development of rapid targeted methods for biomarker identification and a potential diagnosis of gastric cancer.

Liver and urine metabolomics reveal the protective effect of Gandou decoction in copper-laden Hepatolenticular degeneration model rats

Hepatolenticular degeneration (HLD) is an inherited disorder associated with human copper metabolism. Gandou decoction (GDD), a traditional Chinese medicinal formula, has been used as a therapeutic agent for the treatment of HLD in China for decades. Recent pharmacological evaluation in our laboratory has demonstrated that GDD exerts positive and beneficial effects on HLD model rats. However, its underlying therapeutic mechanisms are not yet well understood. To explore the potential therapeutic effects of GDD against HLD, liver and urine metabolomics approach combined with histopathological examination were performed to reveal the underlying mechanisms. Changes in metabolic profiles were estimated by ultra-performance liquid chromatography quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS) coupled with multivariate statistical analyses. The results indicated that GDD could significantly improve liver pathological variations. Moreover, 19 and 11 significantly altered metabolites were found in the liver and urine between the normal and model groups, respectively. After GDD treatment, the levels of all these disordered metabolites showed different degrees of improvement compared with the model group, including lysoPC(18:2), lysoPE(20:2/0:0), PC(18:1/14:1), alpha-linolenic acid, sphinganine, taurochenodesoxycholic acid, tetracosahexaenoic acid, 13-OxoODE, and 13-L-hydroperoxyl inoleic acid. Metabolic pathway enrichment suggested that lipid and oxidative stress metabolism were the two main pathways that participated in copper-laden rat models with GDD administration. This work indicates that GDD could achieve a therapeutic effect on HLD by ameliorating the associated metabolic disturbances.

A novel receptor for platelet-activating factor and lysophosphatidylcholine in Trypanosoma cruzi

The lipid mediators, platelet-activating factor (PAF) and lysophosphatidylcholine (LPC), play relevant pathophysiological roles in Trypanosoma cruzi infection. Several species of LPC, including C18:1 LPC, which mimics the effects of PAF, are synthesized by T. cruzi. The present study identified a receptor in T. cruzi, which was predicted to bind to PAF, and found it to be homologous to members of the progestin and adiponectin family of receptors (PAQRs). We constructed a three-dimensional model of the T. cruzi PAQR (TcPAQR) and performed molecular docking to predict the interactions of the TcPAQR model with C16:0 PAF and C18:1 LPC. We knocked out T. cruzi PAQR (TcPAQR) gene and confirmed the identity of the expressed protein through immunoblotting and immunofluorescence assays using an anti-human PAQR antibody. Wild-type and knockout (KO) parasites were also used to investigate the in vitro cell differentiation and interactions with peritoneal mouse macrophages; TcPAQR KO parasites were unable to react to C16:0 PAF or C18:1 LPC. Our data are highly suggestive that PAF and LPC act through TcPAQR in T. cruzi, triggering its cellular differentiation and ability to infect macrophages.

Mechanism of rutaecarpine on ethanol-induced acute gastric ulcer using integrated metabolomics and network pharmacology

This study was aimed to explore the mechanism of rutaecarpine (RUT) on ethanol-induced gastric ulcer (GU) in mice by integrated approaches. At first, the efficacy was determined through the macroscopic and microscopic state of stomach tissue and the expression levels of GU-related factors. Then, the serum metabolomics method based on UPLC-Q-TOF/MS was used to explore the specific metabolites and metabolic pathways. Finally, the upstream key protein targets of these specific metabolites were analyzed by network pharmacology and verified by PCR to explore the potential mechanism. RUT alleviated the histological and pathological damage of gastric tissue caused by ethanol, and could remarkably ameliorate the level of GU-related factors. Subsequently, a total of 7 potential metabolites involved in 9 metabolic pathways were identified by metabolomics analysis. Then, a 'component-targets-metabolites' interaction network was constructed, and therefore 4 key target proteins (PLA2G1B, PDE5A, MIF and SRC) that may regulate the specific metabolites were obtained. This case was further verified by the results of PCR. ALL the above results strongly demonstrated that RUT exerted a gastroprotective effect against GU. And it is the first time to combine metabolomics combined with network pharmacology to elucidate the mechanism of RUT on GU, which may be related to the regulation of energy metabolism, oxidative stress, and inflammation, and these pathways may be regulated through the upstream protein PLA2G1B, PDE5A, MIF and SRC.

Environmental exposure of northern pike to a primary wastewater effluent: Impact on the lipidomic profile and lipid metabolism

Lipids play important roles in growth, reproduction, locomotion, and migration of fish. Municipal effluents, which are complex mixtures of biological and chemical compounds including flame retardants, have been shown to alter lipid metabletabolism in environmentally and experimentally exposed fish. Down-regulation of several genes coding for fatty acid metabolism enzymes has previously been reported in male northern pike (Esox lucius) collected in the St. Lawrence River (QC, Canada) downstream of a major primary wastewater treatment plant (WWTP) point of discharge. The main objective of this study was to investigate the effects of exposure to the Montreal's WWTP effluent on the lipidomic profile (i.e., fatty acids, acylcarnitines, and phospholipids) as well as the transcription of genes related to lipid metabolism in the liver of northern pike collected upstream and downstream of this WWTP effluent. Halogenated flame retardant concentrations were also determined in pike liver and used as markers of exposure to this effluent. Greater concentrations of saturated and monounsaturated lysophosphatidylcholines (LPCs) and lower concentrations of polyunsaturated LPCs were determined in the liver of pike collected downstream of the WWTP compared to those collected upstream. Lower mRNA levels of peroxisome proliferator-activated receptor alpha (pparα), a major regulator of lipid metabolism, were also measured in pike exposed to Montreal's WWTP effluent. In addition, the relative contributions (%) of LPC 18:2 and LPC14:0, compounds used as markers of obesity and inflammation, were significantly correlated with halogenated flame retardant concentrations and fish girth. Results of the present study suggest that chronic environmental exposure to a primary WWTP effluent can modulate the transcription of genes related to lipid metabolism, and hence affect the hepatic phospholipid composition of pike from the St. Lawrence River.

Macrophage fatty acid metabolism and atherosclerosis: The rise of PUFAs

Among the pathways involved in the regulation of macrophage functions, the metabolism of unsaturated fatty acids is central. Indeed, unsaturated fatty acids act as precursors of bioactive molecules such as prostaglandins, leukotrienes, resolvins and related compounds. As components of phospholipids, they have a pivotal role in cell biology by regulating membrane fluidity and membrane-associated cellular processes. Finally, polyunsaturated fatty acids (PUFAs) are also endowed with ligand properties for numerous membrane or nuclear receptors. Although myeloid cells are dependent on the metabolic context for the uptake of essential FAs, recent studies showed that these cells autonomously handle the synthesis of n-3 and n-6 long chain PUFAs such as arachidonic acid and eicosapentaenoic acid. Moreover, targeting PUFA metabolism in macrophages influences pathological processes, including atherosclerosis, by modulating macrophage functions. Omics evidence also supports a role for macrophage PUFA metabolism in the development of cardiometabolic diseases in humans. Currently, there is a renewed interest in the role of n-3/n-6 PUFAs and their oxygenated derivatives in the onset of atherosclerosis and plaque rupture. Purified n-3 FA supplementation appears as a potential strategy in the treatment and prevention of cardiovascular diseases. In this context, the ability of immune cells to handle and to synthesize very long chain PUFA must absolutely be integrated and better understood.

Mechanism of Curcuma wenyujin Rhizoma on Acute Blood Stasis in Rats Based on a UPLC-Q/TOF-MS Metabolomics and Network Approach

Rhizome of Curcuma wenyujin, which is called EZhu in China, is a traditional Chinese medicine used to treat blood stasis for many years. However, the underlying mechanism of EZhu is not clear at present. In this study, plasma metabolomics combined with network pharmacology were used to elucidate the therapeutic mechanism of EZhu in blood stasis from a metabolic perspective. The results showed that 26 potential metabolite markers of acute blood stasis were screened, and the levels were all reversed to different degrees by EZhu preadministration. Metabolic pathway analysis showed that the improvement of blood stasis by Curcuma wenyujin rhizome was mainly related to lipid metabolism (linoleic acid metabolism, ether lipid metabolism, sphingolipid metabolism, glycerophospholipid metabolism, and arachidonic acid metabolism) and amino acid metabolisms (tryptophan metabolism, lysine degradation). The component-target-pathway network showed that 68 target proteins were associated with 21 chemical components in EZhu. Five metabolic pathways of the network, including linoleic acid metabolism, sphingolipid metabolism, glycerolipid metabolism, arachidonic acid metabolism, and steroid hormone biosynthesis, were consistent with plasma metabolomics results. In conclusion, plasma metabolomics combined with network pharmacology can be helpful to clarify the mechanism of EZhu in improving blood stasis and to provide a literature basis for further research on the therapeutic mechanism of EZhu in clinical practice.

Sanhuang Xiexin Tang Ameliorates Type 2 Diabetic Rats via Modulation of the Metabolic Profiles and NF-κB/PI-3K/Akt Signaling Pathways

Sanhuang Xiexin Tang (SXT), a classic prescription, has been clinically used to cure diabetes for thousands of years, but its mechanism remains unclear. Here, a systematic in-depth research was performed to unravel how it worked by the signaling pathway and metabonomics analysis. Our studies were conducted using high-fat diets (HFD) and streptozocin (STZ)-induced type 2 diabetes mellitus (T2DM) rats. The blood glucose was measured by a glucose-meter. Protein contents were determined by western blotting or ELISA and mRNA expression was identified by RT-PCR analysis. The pathological status of pancreas was assessed by histopathological analysis. Furthermore, Ultra Performance Liquid Chromatography-Quadrupole-Time of Flight/Mass Spectrometry (UPLC-Q-TOF/MS) coupled with multivariate statistical analysis was performed to discover potential biomarkers and the associated pathways. Hyperglycaemia, insulin resistance, dyslipidemia and inflammation in T2DM rats were significantly ameliorated after 7-week oral administration of SXT. The expressions of phosphatidylinositol-3-kinase (PI-3K), protein kinase B (Akt), glucose transporters-4 (GLUT4) Mrna, and p-PI-3K, p-Akt, GLUT4 protein involved in the PI-3K/Akt signaling pathway of T2DM were markedly up-regulated. Further investigation indicated that the perturbance of metabolic profiling in T2DM rats was obviously reversed by SXT and 38 potential biomarkers were screened and identified. Our study might help clarify the mechanism of SXT and provide some evidences for its clinical application in the future.

Crosslink between lipids and acute uveitis: a lipidomic analysis

AIM

To explore the roles of phospholipids and sphingolipids in the inflammatory process of uveitis.

METHODS

Aqueous humor (AH) and the retina were obtained from endotoxin-induced uveitis (EIU) rats during the acute inflammation stage (24h after endotoxin injection). Lipids were extracted using a modified Bligh and Dyer method and subjected to mass spectrometric identification using class-specific lipid standards and ratiometric quantification. Relative intensity analysis was performed to evaluate the amount change of common lipids between the EIU and control groups.

RESULTS

Unique lipid species encompassing all five phospholipid classes were found in both control and the EIU AH and retina. Commensurate with the significantly increased level of lysophospholipids in the EIU AH and retina, we found that the ratio of lysophospholipids to total phospholipids was significantly increased too. We also detected a significant increase in 18:0 lysophosphatidylcholine levels in the EIU group (fold change =6.4 in AH and 3.8 in retina). Cer240, Cer241, and SM240 levels remarkably increased in the EIU AH. Enhanced C12 ceramide-1-phosphate (C12 C-1-P), C16 C-1-P, C24 C-1-P, and upregulated Cer160, Cer240, SM120, and SM240 were found in EIU retina. C-1-P was believed to restore homeostasis by inhibiting nuclear factor kappa B (NF-κB) activation. However, we still found elevated NF-κB levels in the EIU retina.

CONCLUSION

A variety of lipids might have played a critical role in EIU inflammation. Exogenous topical application of these protective lipids or inhibition of these pro-inflammatory lipids may be useful therapeutic strategies for the resolution of EIU.

Comparative Studies on the Lipid Composition of Blood Plum (Haematostaphis Barteri) Pulp and Seed Oils

Background:

Exploring under–utilized plant fruits could be of high significance for food security and nutritional requirements, therefore, it can effectively add to the overall improvement of a nation’s economy. Blood plum (Haematostaphis barteri) is a wild edible vegetable and its fruit contains pulp and oily seed which are edible.

Methods:

A study was carried out to determine fatty acid profile, phospholipid and phytosterol contents as well as some physicochemical parameters of pulp and seed oils of Haematostaphis barteri (popularly known as blood plum) using standard analytical techniques.

Results:

The most concentrated fatty acids were palmitic acid (15.34%) < oleic acid (22.31%) < linoleic acid (50.56%) for the pulp oil while that of seed oil were oleic acid (12.34%) < palmitic acid (25.37%) < linoleic acid (38.87%). Arachidic, behenic, lignoceric and palmitoleic acids were all present in small quantities with none of them recording up to 1.0% in either of the samples. Lauric was determined but not detected in the pulp oil. The fatty acid composition of pulp and seed oils contained a healthy mixture of all the types of saturated and unsaturated fatty acids. The value of polyunsaturated/saturated index (P/S) which is associated to the impact on human health was higher in the pulp oil (2.47). Phospatidylinositol had the highest content (17.69 mg/100g) in the pulp oil while the highest content in seed oil was phosphatidylcholine (351.82 mg/100g). The total phytosterols for pulp and seed oils were 17.09 and 436.37 mg/100g, respectively. The results of some physicochemical parameters of pulp and seed oils were colour (light amber yellow and pale yellow), kinematic viscosity (9.15 and 10.62 mm²/s), specific gravity (0.92 and 0.92), unsaponifiable matter (1.63 and 2.54%), flash point 29.00 and 295.00^oC), saponification value (189.40 and 190.22 mg KOH/g), peroxide value (8.15 and 9.20 meq O₂/kg), iodine value (94.24 and 122.42 mg of I/100 g) and acid value (16.50 and 24.00 mg KOH/g), respectively.

Conclusion:

Generally, high percentage PUFA and low value of cholesterol may make either of the sample oils, a good food source on health wise basis. It was also revealed that both sample oils may be developed into a commercial product for use in food products.

Probiotic Modulation of Innate Cell Pathogen Sensing and Signaling Events

There is a growing body of evidence documenting probiotic bacteria to have a beneficial effect to the host through their ability to modulate the mucosal immune system. Many probiotic bacteria can be considered to act as either immune activators or immune suppressors, which have appreciable influence on homeostasis, inflammatory- and suppressive-immunopathology. What is becoming apparent is the ability of these probiotics to modulate innate immune responses via direct or indirect effects on the signaling pathways that drive these activatory or suppressive/tolerogenic mechanisms. This review will focus on the immunomodulatory role of probiotics on signaling pathways in innate immune cells: from positive to negative regulation associated with innate immune cells driving gut mucosal functionality. Research investigations have shown probiotics to modulate innate functionality in many ways including, receptor antagonism, receptor expression, binding to and expression of adaptor proteins, expression of negative regulatory signal molecules, induction of micro-RNAs, endotoxin tolerisation and finally, the secretion of immunomodulatory proteins, lipids and metabolites. The detailed understanding of the immunomodulatory signaling effects of probiotic strains will facilitate strain-specific selective manipulation of innate cell signal mechanisms in the modulation of mucosal adjuvanticity, immune deviation and tolerisation in both healthy subjects and patients with inflammatory and suppressive pathology.

Growth factors regulate phospholipid biosynthesis in human fibroblast-like synoviocytes obtained from osteoarthritic knees

Elevated levels of growth factors and phospholipids (PLs) have been found in osteoarthritic synovial fluid (SF), although the metabolic regulation of PLs is currently unknown. This study aimed to determine the effects of growth factors on the biosynthesis of PLs by fibroblast-like synoviocytes (FLS) obtained from human osteoarthritic knee joints. Electrospray ionization tandem mass spectrometry was applied to analyse the newly synthesized PLs. In the presence of stable isotope-labelled PL precursors, cultured FLS were treated with either transforming growth factor-β1 (TGF-β1), bone morphogenetic protein (BMP)-2, BMP-4, BMP-7 or insulin-like growth factor-1 (IGF-1) alone or in combination with specific inhibitors of cell signalling pathways. TGF-β1 and IGF-1 markedly stimulated the biosynthesis of phosphatidylcholine (PC) before sphingomyelin (SM) and lysophosphatidylcholine (LPC) species were stimulated. BMPs elaborated less pronounced effects. The BMPs tested have different potentials to induce the biosynthesis of phosphatidylethanolamine (PE) and PE-based plasmalogens. Our study shows for the first time that TGF-β1 and IGF-1 substantially regulate the biosynthesis of PC, SM and LPC in human FLS. The functional consequences of elevated levels of PLs require additional study. The BMPs tested may be joint protective in that they upregulate PE-based plasmalogens that function as endogenous antioxidants against reactive oxygen species.

UPLC-Q-TOF/MS-based urine and plasma metabonomics study on the ameliorative effects of aspirin eugenol ester in hyperlipidemia rats

The main objective of this study was to investigate the ameliorative effects of aspirin eugenol ester (AEE) in hyperlipidemic rat. After five-week oral administration of AEE in high fat diet (HFD)-induced hyperlipidemic rats, the impact of AEE on plasma and urine metabonomics was investigated to explore the underlying mechanism by UPLC-Q-TOF/MS analysis. Blood lipid levels and histopathological changes of liver, stomach and duodenum were also evaluated after AEE treatment. Without obvious gastrointestinal (GI) side effects, AEE significantly relieved fatty degeneration of liver and reduced triglyceride (TG), low density lipoprotein (LDL) and total cholesterol (TCH) (P<0.01). Clear separations of metabolic profiles were observed among control, model and AEE groups by using principal component analysis (PCA) and orthogonal partial least-squares-discriminate analysis (OPLS-DA). 16 endogenous metabolites in plasma and 18 endogenous metabolites in urine involved in glycerophospholipid metabolism, fatty acid metabolism, fatty acid beta-oxidation, amino acid metabolism, TCA cycle, sphingolipid metabolism, gut microflora and pyrimidine metabolism were considered as potential biomarkers of hyperlipidemia and be regulated by AEE administration. It might be concluded that AEE was a promising drug candidate for hyperlipidemia treatment. These findings could contribute to the understanding of action mechanisms of AEE and provide evidence for further studies.

Serum metabolomics analysis reveals that obvious cardioprotective effects of low dose Sini decoction against isoproterenol-induced myocardial injury in rats

BACKGROUND

Sini decoction (SND) is used for cardiovascular disease over thousands of years in China. However, it is still lacking of dose-response relationship of SND in cardiovascular disease at the metabolic level.

PURPOSE

The present study is designed to explore the cardioprotective effects of different dosages of SND pretreatment on the isoproterenol (ISO)-induced myocardial injury and elucidate the mechanism underlying this protective effect.

METHODS

The cardioprotective effects of different dosages of SND pretreatment on the isoproterenol-induced myocardial injury were compared through a serum metabolomics approach based on ultraperformance liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF-MS). In addition, the cardioprotective effects were evaluated by serum biochemical analysis and histopathological examination of myocardial tissue. Finally, in view of the fact that these perturbed bile acid and phospholipid metabolisms are connected with NF-κB signaling pathway, nuclear expression of NF-κB p65 and the activation of NF-κB were analyzed by immunohistochemistry, immunoblotting and electrophoretic mobility shift assay (EMSA), respectively.

RESULTS

The cardioprotective effect was observed in SND pretreatment groups, especially in low dosage SND group. The results of serum enzyme activities and histopathology were consistent with the above effect. Meanwhile, fifteen latent biomarker candidates were identified involving glucose, phospholipid, bile acid and amino acid metabolisms. Among them, five bile acids including ursodeoxycholic acid, murideoxycholic acid, muricholic acid, hyodeoxycholic acid and cholic acid, were for the first time identified as latent pathological biomarkers related to ISO-induced myocardial injury. Further, different dose SND groups exerted different of inhibition degrees to the activation of NF-κB, which was obvious in the SND-L group.

CONCLUSION

The results revealed that Sini decoction protreatment protects myocardium better at a low dose level and one of possible cardioprotective mechanisms is modulating NF-κB signaling pathway against isoproterenol-induced myocardial injury through regulating phospholipid and bile acid metabolisms.

Lipidomics to investigate the pharmacologic mechanisms of ginkgo folium in the hyperuricemic rat model

Hyperuricemia caused by purine metabolic abnormalities is reported to have close correlation with lipid metabolic disorders. Ginkgo folium, a frequently-used lipid-lowering medicine, has significant anti-hyperuricemia effects. However, it is poorly known about the interaction between lowering uric acid and regulation of lipid metabolic disorders. In this study, hyperuricemic rat model was induced by orally administration with fructose. Ultra-performance liquid chromatography-quadrupole-time-of-flight mass spectrometry (UPLC-Q-TOF/MS) combined with pattern recognition approaches were used to determine different lipid metabolites in serum of control group, model group, and different doses of ginkgo folium groups. Principal component analysis (PCA) was applied to analyze the MS data to assess the establishment of model, partial least squares-discriminate analysis (PLS-DA) and independent samples T-test were performed to indicate the differences between different groups of rats and to find biomarkers. Metabolomics pathway analysis (MetPA) was introduced to reveal the pharmacologic mechanisms of ginkgo folium. 19 potential biomarkers associated with hyperuricemia were found. After intervened by ginkgo folium, these biomarkers were returning to normal level. Among these biomarkers, 13 lipid biomarkers were significantly reversed. Ginkgo filum can lower uric acid via adjusting back the level of PCs and LPCs, which suggested that its treatment mechanisms may be related to reducing the activity of PLA2. In sum, the lipidomics analysis in the system level have enhanced our understanding to pathogenesis of hyperuricemia and the results suggested that ginkgo folium could alleviate the abnormal metabolic status of hyperuricemia. These results demonstrated a new mechanism for lowering uric acid, which was helpful to the early treatment for hyperuricemia.

Lipid response patterns in acute phase paediatric Plasmodium falciparum malaria

INTRODUCTION

Several studies have observed serum lipid changes during malaria infection in humans. All of them were focused at analysis of lipoproteins, not specific lipid molecules. The aim of our study was to identify novel patterns of lipid species in malaria infected patients using lipidomics profiling, to enhance diagnosis of malaria and to evaluate biochemical pathways activated during parasite infection.

METHODS

Using a multivariate characterization approach, 60 samples were representatively selected, 20 from each category (mild, severe and controls) of the 690 study participants between age of 0.5-6 years. Lipids from patient's plasma were extracted with chloroform/methanol mixture and subjected to lipid profiling with application of the LCMS-QTOF method.

RESULTS

We observed a structured plasma lipid response among the malaria-infected patients as compared to healthy controls, demonstrated by higher levels of a majority of plasma lipids with the exception of even-chain length lysophosphatidylcholines and triglycerides with lower mass and higher saturation of the fatty acid chains. An inverse lipid profile relationship was observed when plasma lipids were correlated to parasitaemia.

CONCLUSIONS

This study demonstrates how mapping the full physiological lipid response in plasma from malaria-infected individuals can be used to understand biochemical processes during infection. It also gives insights to how the levels of these molecules relate to acute immune responses.

Metabolite and Lipid Profiling of Biobank Plasma Samples Collected Prior to Onset of Rheumatoid Arthritis

OBJECTIVE

The early diagnosis of rheumatoid arthritis (RA) is desirable to install treatment to prevent disease progression and joint destruction. Autoantibodies and immunological markers pre-date the onset of symptoms by years albeit not all patients will present these factors, even at disease onset. Additional biomarkers would be of high value to improve early diagnosis and understanding of the process, leading to disease development.

METHODS

Plasma samples donated before the onset of RA were identified in the Biobank of Northern Sweden, a collection within national health survey programs. Thirty samples from pre-symptomatic individuals and nineteen from controls were subjected to liquid chromatography-mass spectrometry (LCMS) metabolite and lipid profiling. Lipid and metabolite profiles discriminating samples from pre-symptomatic individuals from controls were identified after univariate and multivariate OPLS-DA based analyses.

RESULTS

The OPLS-DA models including pre-symptomatic individuals and controls identified profiles differentiating between the groups that was characterized by lower levels of acyl-carnitines and fatty acids, with higher levels of lysophospatidylcholines (LPCs) and metabolites from tryptophan metabolism in pre-symptomatic individuals compared with controls. Lipid profiling showed that the majority of phospholipids and sphingomyelins were at higher levels in pre-symptomatic individuals in comparison with controls.

CONCLUSIONS

Our LCMS based approach demonstrated that there are changes in small molecule and lipid profiles detectable in plasma samples collected from the pre-symptomatic individuals who subsequently developed RA, which point to an up-regulation of levels of lysophospatidylcholines, and of tryptophan metabolism, perturbation of fatty acid beta-oxidation and increased oxidative stress in pre-symptomatic individuals' years before onset of symptoms.

Metabolomic studies of human gastric cancer: Review

Metabolomics is a field of study in systems biology that involves the identification and quantification of metabolites present in a biological system. Analyzing metabolic differences between unperturbed and perturbed networks, such as cancerous and non-cancerous samples, can provide insight into underlying disease pathology, disease prognosis and diagnosis. Despite the large number of review articles concerning metabolomics and its application in cancer research, biomarker and drug discovery, these reviews do not focus on a specific type of cancer. Metabolomics may provide biomarkers useful for identification of early stage gastric cancer, potentially addressing an important clinical need. Here, we present a short review on metabolomics as a tool for biomarker discovery in human gastric cancer, with a primary focus on its use as a predictor of anticancer drug chemosensitivity, diagnosis, prognosis, and metastasis.

Liver x receptor regulates arachidonic acid distribution and eicosanoid release in human macrophages: a key role for lysophosphatidylcholine acyltransferase 3

OBJECTIVE

Liver X receptors (LXRs) are oxysterol-activated nuclear receptors that are highly expressed in macrophages and regulate lipid homeostasis and inflammation. Among putative LXR target genes, lysophosphatidylcholine acyltransferase 3 (LPCAT3) involved in the Lands cycle controls the fatty acid composition at the sn-2 position of glycerophospholipids and, therefore, the availability of fatty acids, such as arachidonic acid (AA), used for eicosanoid synthesis. The aim of our study was to determine whether LXRs could regulate the Lands cycle in human macrophages, to assess the consequences in terms of lipid composition and inflammatory response, and to work out the relative contribution of LPCAT3 to the observed changes.

APPROACH AND RESULTS

Transcriptomic analysis revealed that LPCAT3 was upregulated by LXR agonists in human macrophages. Accordingly, LXR stimulation significantly increased lysophospholipid acyltransferase activity catalyzed by LPCAT3. Lipidomic analysis demonstrated that LXR activation increased the AA content in the polar lipid fraction, specifically in phosphatidylcholines. The LXR-mediated effects on AA distribution were abolished by LPCAT3 silencing, and a redistribution of AA toward the neutral lipid fraction was observed in this context. Finally, we observed that preconditioning of human macrophages by LXR agonist treatment increased the release of arachidonate-derived eicosanoids, such as prostaglandin E2 and thromboxane after lipopolysaccharide stimulation, with a significant attenuation by LPCAT3 silencing.

CONCLUSIONS

Altogether, our data demonstrate that the LXR-mediated induction of LPCAT3 primes human macrophages for subsequent eicosanoid secretion by increasing the pool of AA, which can be mobilized from phospholipids.

Aging bone marrow mesenchymal stromal cells have altered membrane glycerophospholipid composition and functionality

Human mesenchymal stem/stromal cells (hMSC) are increasingly used in advanced cellular therapies. The clinical use of hMSCs demands sequential cell expansions. As it is well established that membrane glycerophospholipids (GPL) provide precursors for signaling lipids that modulate cellular functions, we studied the effect of the donor's age and cell doublings on the GPL profile of human bone marrow MSC (hBMSC). The hBMSCs, which were harvested from five young and five old adults, showed clear compositional changes during expansion seen at the level of lipid classes, lipid species, and acyl chains. The ratio of phosphatidylinositol to phosphatidylserine increased toward the late-passage samples. Furthermore, 20:4n-6-containing species of phosphatidylcholine and phosphatidylethanolamine accumulated while the species containing monounsaturated fatty acids (FA) decreased during passaging. Additionally, in the total FA pool of the cells, 20:4n-6 increased, which happened at the expense of n-3 polyunsaturated FAs, especially 22:6n-3. The GPL and FA correlated with the decreased immunosuppressive capacity of hBMSCs during expansion. Our observations were further supported by alterations in the gene expression levels of several enzymes involved in lipid metabolism and immunomodulation. The results show that extensive expansion of hBMSCs harmfully modulates membrane GPLs, affecting lipid signaling and eventually impairing functionality.

Therapeutic options for transfusion related acute lung injury; the potential of the G2A receptor

Priming of polymorphonuclear leukocytes (PMNs) enhances their adhesion to endothelium, the release of their granule content and their production of reactive oxygen species. These effects are etiological in transfusion related acute lung injury (TRALI) and many clinically important mediators of TRALI prime PMNs. A priming activity that develops over time in stored blood products has been shown to be due to the accumulation of lysophospatidylcholines (lyso-PCs) and has been found to be related clinically to TRALI. Lyso- PCs prime PMNs activating the G2A receptor and several inhibitors of this receptor, which could potentially be therapeutic in TRALI, have been identified. Recent work has described early steps in the signaling from the G2A receptor which has revealed potential targets for novel antagonists of lyso-PC mediated priming via G2A. Additionally, characterization of the process by which lyso-PCs are generated in stored blood products could allow development of inhibitors and additive solutions to block their formation in the first place.

Emerging roles for lysophosphatidylserine in resolution of inflammation

Despite overlapping structural aspects with other phospholipids, lysophosphatidylserine (lysoPS), the monoacyl derivative of phosphatidylserine (diacylPS), appears to exert unique signaling characteristics important in both the early stages of initiating acute inflammation and in the orchestration of its resolution. LysoPS has long been known as a signaling phospholipid in mast cell biology, markedly enhancing stimulated histamine release and eicosanoid production. More recently, there has been a resurgence of interest in lysoPS as new roles in the promotion of phagocytosis of apoptotic cells, so-called efferocytosis, and resolution of inflammation have been identified. With regard to the latter, lysoPS generated in/on activated or aged apoptotic neutrophils enhances their clearance by macrophages via signaling through the macrophage G-protein coupled receptor G2A. In macrophages, this early acting pathway results in PKA-dependent augmentation of Rac1 activity via increased production of PGE₂ and cAMP. As such, macrophages stimulated with lysoPS demonstrate significantly increased efferocytic capacity necessary to clear large numbers of recruited neutrophils typical of acute inflammation. Given that clearance of these cells is critical for restoration of tissue function, lysoPS, as a pro-resolving lipid mediator, is hypothesized to play a key role in promoting timely resolution of inflammation. This article will review our current knowledge of lysoPS biology including receptor signaling and mechanisms of generation as well as summarize the more recent evidence of its expanding roles in inflammation.

The split personality of NKT cells in malignancy, autoimmune and allergic disorders

NKT cells are a heterogeneous subset of specialized, self-reactive T cells, with innate and adaptive immune properties, which allow them to bridge innate and adaptive immunity and profoundly influence autoimmune and malignant disease outcomes. NKT cells mediate these activities through their ability to rapidly express pro- and anti-inflammatory cytokines that influence the type and magnitude of the immune response. Not only do NKT cells regulate the functions of other cell types, but experimental evidence has found NKT cell subsets can modulate the functions of other NKT subsets. Depending on underlying mechanisms, NKT cells can inhibit or exacerbate autoimmunity and malignancy, making them potential targets for disease intervention. NKT cells can respond to foreign and endogenous antigenic glycolipid signals that are expressed during pathogenic invasion or ongoing inflammation, respectively, allowing them to rapidly react to and influence a broad array of diseases. In this article we review the unique development and activation pathways of NKT cells and focus on how these attributes augment or exacerbate autoimmune disorders and malignancy. We also examine the growing evidence that NKT cells are involved in liver inflammatory conditions that can contribute to the development of malignancy.

Mechanisms for anti-inflammatory effects of 1-[15(S)-hydroxyeicosapentaenoyl] lysophosphatidylcholine, administered intraperitoneally, in zymosan A-induced peritonitis

BACKGROUND AND PURPOSE

Lysophosphatidylcholines (lysoPCs) with polyunsaturated acyl chains are known to exert anti-inflammatory actions. 15-Lipoxygeanation is crucial for anti-inflammatory action of polyunsaturated acylated lysoPCs. Here, the anti-inflammatory actions of 1-(15-hydroxyeicosapentaenoyl)-lysoPC (15-HEPE-lysoPC) and its derivatives were examined in a mechanistic analysis.

EXPERIMENTAL APPROACH

Anti-inflammatory actions of 15-HEPE-lysoPC in zymosan A-induced peritonitis of mice were examined by measuring plasma leakage and leucocyte infiltration, and determining levels of lipid mediators or cytokines.

KEY RESULTS

When each lysoPC, administered i.v., was assessed for its ability to suppress zymosan A-induced plasma leakage, 15-HEPE-lysoPC was found to be more potent than 1-(15-hydroperoxyeicosapentaenoyl)-lysoPC or 1-eicosapentaenoyl-lysoPC. Separately, i.p. administration of 15-HEPE-lysoPC markedly inhibited plasma leakage, in contrast to 15-HEPE, which had only a small effect. 15-HEPE-lysoPC also decreased leucocyte infiltration. Moreover, it reduced the formation of LTC₄ and LTB₄, 5-lipoxygenation products, as well as the levels of pro-inflammatory cytokines. The time-course study indicated that 15-HEPE-lysoPC might participate in both the early inflammatory phase and resolution phase. Additionally, 15-HEPE-lysoPC administration caused a partial suppression of LTC₄-induced plasma leakage and LTB₄-induced leucocyte infiltration. In the metabolism study, peritoneal exudate was shown to contain lysoPC-hydrolysing activity, crucial for anti-inflammatory activity, and a system capable of generating lipoxin A from 15-hydroxy eicosanoid precursor.

CONCLUSIONS AND IMPLICATIONS

15-HEPE-lysoPC, a precursor for 15-HEPE in target cells, induced anti-inflammatory actions by inhibiting the formation of pro-inflammatory leukotrienes and cytokines, and by enhancing the formation of lipoxin A. 15-HEPE-lysoPC might be one of many potent anti-inflammatory lipids in vivo.

A metabonomic approach to chemosensitivity prediction of cisplatin plus 5-fluorouracil in a human xenograft model of gastric cancer

The prediction of chemosensitivity is a challenging problem in the management of cancer. In the present study, a metabonomic approach was proposed to assess the feasibility of chemosensitivity prediction in a human xenograft model of gastric cancer. BALB/c-nu/nu mice were transplanted with MKN-45 cell line to establish the xenograft model. The mice were then randomized into treatment group (cisplatin and 5-fluorouracil) and control group (0.9% sodium chloride), and their plasma were collected before treatment. Metabolic profiles of all plasma samples were acquired by using high-performance liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer (HPLC/Q-TOF-MS). Based on the data of metabolic profiles and k-Nearest Neighbor algorithm, a prediction model for chemosensitivity was developed and an average accuracy of 90.4% was achieved. In addition, a series of endogenous metabolites, including 1-acyl-lysophosphatidycholines, polyunsaturated fatty acids and their derivatives, were determined as potential indicators of chemosensitivity. In conclusion, our results suggest that the proposed metabonomic approach allows effective chemosensitivity prediction in human xenograft model of gastric cancer. The approach presents a new concept in the chemosensitivtiy prediction of cancer and is expected to be developed as a powerful tool in the personalized cancer therapy.

Phosphatidylcholine as a constituent in the colonic mucosal barrier--physiological and clinical relevance

Phosphatidylcholine (PC) is an important constituent of the gastrointestinal tract. PC molecules are not only important in intestinal cell membranes but also receiving increasing attention as protective agents in the gastrointestinal barrier. They are largely responsible for establishing the hydrophobic surface of the colon. Decreased phospholipids in colonic mucus could be linked to the pathogenesis of ulcerative colitis, a chronic inflammatory bowel disease. Clinical studies revealed that therapeutic addition of PC to the colonic mucus of these patients alleviated the inflammatory activity. This positive role is still elusive, however, we hypothesized that luminal PC has two possible functions: first, it is essential for surface hydrophobicity, and second, it is integrated into the plasma membrane of enterocytes and it modulates the signaling state of the mucosa. The membrane structure and lipid composition of cells is a regulatory component of the inflammatory signaling pathways. In this perspective, we will shortly summarize what is known about the localization and protective properties of PC in the colonic mucosa before turning to its evident medical importance. We will discuss how PC contributes to our understanding of the pathogenesis of ulcerative colitis and how reinforcing the luminal phospholipid monolayer can be used as a therapeutic concept in humans.

ATP-binding membrane cassette transporter A1 (ABCA1): a possible link between inflammation and reverse cholesterol transport

Atherosclerosis is characterized by a chronic inflammatory condition that involves numerous cellular and molecular inflammatory components. A wide array of inflammatory mediators, such as cytokines and proteins produced by macrophages and other cells, play a critical role in the development and progression of the disease. ATP-binding membrane cassette transporter A1 (ABCA1) is crucial for cellular cholesterol efflux and reverse cholesterol transport (RCT) and is also identified as an important target in antiatherosclerosis treatment. Evidence from several recent studies indicates that inflammation, along with other atherogenic-related mediators, plays distinct regulating roles in ABCA1 expression. Proatherogenic cytokines such as interferon (IFN)-γ and interleukin (IL)-1β have been shown to inhibit the expression of ABCA1, while antiatherogenic cytokines, including IL-10 and transforming growth factor (TGF)-β1, have been shown to promote the expression of ABCA1. Moreover, some cytokines such as tumor necrosis factor (TNF)-α seem to regulate ABCA1 expression in species-specific and dose-dependent manners. Inflammatory proteins such as C-reactive protein (CRP) and cyclooxygenase (COX)-2 are likely to inhibit ABCA1 expression during inflammation, and inflammation induced by lipopolysaccharide (LPS) was also found to block the expression of ABCA1. Interestingly, recent experiments revealed ABCA1 can function as an antiinflammatory receptor to suppress the expression of inflammatory factors, suggesting that ABCA1 may be the molecular basis for the interaction between inflammation and RCT. This review aims to summarize recent findings on the role of inflammatory cytokines, inflammatory proteins, inflammatory lipids, and the endotoxin-mediated inflammatory process in expression of ABCA1. Also covered is the current understanding of the function of ABCA1 in modulating the immune response and inflammation through its direct and indirect antiinflammatory mechanisms including lipid transport, high-density lipoprotein (HDL) formation and apoptosis.

G2A and LPC: regulatory functions in immunity

The G2A receptor was originally identified by virtue of its transcriptional induction in murine B lymphoid cells in response to oncogenic transformation and treatment with various DNA-damaging agents. While preliminary characterization of cellular responses to G2A overexpression in fibroblastic cell lines suggested that this receptor may negatively regulate cell growth under conditions of proliferative and genotoxic stress, subsequent studies driven by the discovery of lysophosphatidylcholine (LPC) as a regulator of G2A signaling in immunoregulatory cells point to an important role for this receptor in innate and adaptive immunity.